Scavenge N – cover crops can scavenge or “trap” residual soil nitrate to prevent it from leaching into drainage water. This protects water quality, and some of the scavenged N will be available to succeeding cash crops while the rest helps build soil organic matter.
Produce N – Legumes “fix” atmospheric nitrogen for their own use. After the legume cover crop is terminated, much of this N will be released as the residues decompose, providing available N to succeeding crops.
Prevent Erosion – The classic use of cover crops is to cover the soil surface to protect against both water and wind erosion, thus conserving the soil resource base.
Build Soil Quality – Cover crops improve soil physical properties, increase soil organic matter, and increase soil biological activity. Fibrous roots build soil aggregation and deep-rooted crops improve permeability. Some tap-rooted crops help break up compacted layers, improving water flow, aeration, and cash-crop rooting. Cover crops stimulate soil biological activity by providing additional food in the cover crop shoot and root residues. Cover crops left as a mulch at the soil surface can also conserve soil moisture for later use by the cash crop.
Suppress Weeds – Some cover crops can suppress weeds by competition, shading, or allelopathy. Unfortunately, some cover crops can also become weeds in subsequent cash crops if not carefully managed.
Recycle Nutrients – Although N is the usual focus, cover crops may also help recycle other nutrients by reducing erosion, building soil organic matter, and increasing soil biological activity.
Protect Water Quality – cover crops scavenge residual soil N, thereby reducing N losses to drainage water. They also reduce erosion and the losses of phosphorus and pesticides bound to the sediments.
Enhance Wildlife Habitat – cover crops can provide water, cover, and food for birds and other wildlife and increase landscape diversity.